The invention relates generally to the coking of coal.
The coking of dry or preheated coal such as, for instance, coal which has been heated to the temperature range of 150.degree. to 250.degree. C prior to coking, provides the advantage that savings in high-priced fuel may be realized during the coking process. The reason is that lower priced fuels may be used for the preheating operation than for the coking operation. Moreover, the use of preheated coking coal permits coke of higher quality to be produced. In particular, the coke produced from coal which has been preheated has a larger particle size and a greater resistance to abrasion than the coke produced from coal which has not been preheated. Consequently, a preheating operation makes it possible to use coal of poorer coking quality than would otherwise be required during a coke production process.
There is, however, a disadvantageous aspect associated with the introduction of dry, preheated coal into the coke ovens and this resides in the marked generation of coal dust which occurs interiorly of the ovens. The dust escapes from the ovens into the collecting means and, in the latter, leads to the formation of deposits or blockages which are difficult to remove.
It has already been proposed to add 0.5 to 3 percent by weight of residual oils having a Baume density of 6.degree.-25.degree., or of residual oils in admixture with pitch, to the preheated coal, the purpose being to reduce the danger of ignition and explosion. The action of these additions is, however, unreliable since a uniform distribution of the residual oils over the coal, particularly when the oils are mixed with pitch, is extremely difficult to achieve. The reason for this resides in that the additions outlined above have a relatively poor wetting effect on the hot coal. Accordingly, these additions have little effect as binding agents for the coal dust and, if any such effect is to be achieved, it is necessary to provide special mixers.